In accordance with the welded structures on the mount-box of jet engine case

the finate element model(FEM) models of four kinds of welded joints including normal butt welding

dislocation butt welding

non-isopachous butt welding and new material butt welding are established.Stress analysis of these butt welding's is carried out by means of the finite element analysis software ANSYS

and the stress-concentration-coefficient of the four welded joints is obtained.The stress fatigue tests are implemented on the four kinds of butt welding pieces.The experimental results are analyzed and compared using the method of group comparison

and the fatigue life for the four kinds of butt welding is predicted.The result of the scanning electron microscope(SEM) fracture analysis indicated that the defection in the stress-concentrated area is the dominant factor to affect the fatigue life of the weld-joint.